The International Union of Immunological Societies (IUIS) mourns the passing of Georg Friedrich (Fritz) Melchers, a distinguished immunologist and a former president of IUIS, who passed away on February 24, 2025. Fritz was not only a brilliant scientist but also a visionary leader in the field of immunology. His contributions to B cell biology, particularly his discovery of the “surrogate light chain,” have been fundamental to our understanding of antibody formation. As Director of the Basel Institute for Immunology (1980–2001), he fostered a thriving research environment that produced Nobel laureates and pioneering discoveries. Later, he continued his impactful work at the Max Planck Institute for Infection Biology in Berlin and as Leibniz Chair at the DRFZ, where he inspired generations of scientists.

Beyond his scientific achievements, Fritz was a passionate mentor, an exceptional organizer, and a key figure in shaping the global immunology community. He played a pivotal role in the 7th International Congress on Immunology in Berlin in 1989 and contributed to numerous scientific advisory boards and academies. As a founding figure of the DRFZ, he championed an open and collaborative research culture that continues to influence immunology today. His legacy is one of deep scientific curiosity, dedication, and excellence, and he will be remembered as both a pioneer and a role model for the immunologists of the future.